They are found from Trinidad to northern Argentina, being absent only in Ecuador and Chile, highland regions, and the southernmost part of South America.

[1][5] These frogs have several adaptations to aquatic life, such as protuberant eyes, robust hind limbs, and fully webbed feet.

What sets them apart is their tadpoles that start out as fairly normal, but continue growing until reaching gigantic sizes, sometimes as much as 22–27 cm (9–11 in) in length in P. paradoxa and P.

[3][5][13] Pseudis is closely related to a second genus, Lysapsus, that lacks giant tadpoles and in which adults are smaller, up to 2.5 cm (1.0 in).

[5] The phylogenetic position of frogs currently included in the genus Pseudis in relation to other anurans was for a long time a matter of debate.

They have been placed in Ranidae, Leptodactylidae,[20] Hylidae,[21] and as their own family Pseudidae[22] This results from their highly derived body plan for a hylid frog due to their mostly aquatic habits.

Recent morphological[23] and molecular[24] phylogenetic reconstructions have unambiguously placed them within the subfamily Hylinae with Scarthyla as a sister group.